The invention relates to a method for operating a condenser tumble dryer with a drying chamber for the objects to be dried, a process air circuit in which a heating element for heating the process air is situated and the heated air is conducted over the items to be dried using a fan, a heat pump circuit with an evaporator, a compressor and a condenser, as well as sensors for determining the humidity in the objects to be dried, as well as to a condenser tumble dryer that is suitable for said method. The method is suitable for disinfection of the objects, which are especially items of laundry.
Tumble dryers which function on the basis of condensing from the process air taken away from the laundry the moisture evaporated from the laundry by the warm process air—known as condenser dryers—do not need a vented air hose and are very popular since they can be used in an internal bathroom or in a washing and cooking area of a larger residential complex. This applies both to tumble dryers designed specifically for drying laundry and also to so-called washer/dryers, i.e. appliances that can both wash the laundry and also dry it. Any subsequent reference to a tumble dryer or condenser dryer thus applies both to an appliance designed only for drying as well as an appliance designed equally for washing and drying.
In a condenser tumble dryer air (so-called process air) is directed via a fan over a heating element into a drum containing items of wet laundry acting as a drying chamber. The hot air takes up humidity from the items of laundry to be dried. After passing through the drum, the now moist process air is directed into a heat exchanger, upstream of which a lint filter is normally connected.
The moist air is cooled down in the heat exchanger, typically by a separately directed stream of cool air, so that the humidity contained in the moist process air condenses. The water arising from this process is subsequently generally collected in a suitable container and the cooled and dried air is fed once again to the heating element and subsequently to the drum.
This drying process is very energy-intensive, since the heat extracted in the cooling of the process air in the heat exchanger is lost whenever this heat is taken away in a cooling air stream. By using a heat pump this energy loss can be greatly reduced. In such cases the well-known compressor heat pump is used, in which a working or cooling medium to be condensed and evaporated in cycles circulates and which has numerous applications for cooling or air conditioning. For a condenser tumble dryer equipped with such a heat pump the warm process air laden with moisture is essentially cooled in a first heat exchanger of the heat pump, especially an evaporator, where the transferred heat is used for evaporating a coolant employed in the heat pump. Such coolant evaporated as a result of being heated up is fed via a compressor to a second heat exchanger, referred to here and below as an evaporator, where, as a result of the condensation of the gaseous coolant, heat is released which is used in its turn for heating up the process air before it enters the drum. The condensed coolant passes via a choke, which lowers its pressure, back to the evaporator in order to evaporate there while again taking up heat from the process air.
In a condenser dryer with a compressor heat pump a temperature of only 50° C. to 60° C. occurs in the drying chamber as a result of the process, which is generally not sufficient for the disinfection of the laundry. The disinfection in condenser dryers, especially the disinfection of items of laundry would however basically be possible without any problems were the drying chamber and thereby the items of laundry held in it to be kept for a sufficiently long period at a temperature of over 70° C.